Compounds having an unsaturated group and an isocyanate group in the molecule, with examples including 2-isocyanatoethyl methacrylate (Karenz MOI manufactured by Showa Denko K.K.), are known as monomers having polymerizable functional groups with different polymerization properties in the molecule. Such monomers having in the molecule two functional groups with different polymerization properties, namely, an unsaturated group and an isocyanate group, are compounds that are useful as raw materials for resins in the fields of coating materials, UV curable paints, thermosetting paints, forming materials, adhesives, inks, resists, optical materials, stereolithography resins, printing matrix materials, dental materials, polymer battery materials and the like.
For the production of such compounds, U.S. Pat. No. 2,821,544 (Patent Document 1) discloses a method for preparing an aliphatic compound containing an unsaturated group and an isocyanate group in the molecule. Specifically, the method comprises reacting an unsaturated carboxylic acid chloride with an amino alcohol hydrochloride to synthesize an unsaturated carboxylic acid aminoalkyl ester hydrochloride, and thereafter reacting it with carbonyl chloride to afford an unsaturated carboxylic acid isocyanatoalkyl ester.
The method of Patent Document 1, however, causes problems that the reaction yield is low and the purification entails undue work, because the compound obtained contains much byproducts assumed to be based on the unsaturated group (for example, addition of HCl to the unsaturated group).
For the meanwhile, there have recently been demands for high refractive index and high heat resistance in the optical field and the like, and monomers having an aromatic ring in the molecule have been desired. Such compounds include 3-isopropenyl-α,α-dimethylbenzyl isocyanate compound that has an unsaturated group and an isocyanate group, and an aromatic ring in the molecule, as disclosed in JP-A-2003-12632 (Patent Document 2).
However, the compound of Patent Document 2 has the unsaturated group at the benzyl position, and therefore a cured product of the compound shows low weathering resistance and the reacting rate of the isocyanate group is low.
With respect to the adducts of isocyanate compounds as discussed above, JP-A-2000-086302 (Patent Document 3) discloses a composition including a polyester polyurethane (meth)acrylate oligomer. The oligomer is obtained by urethanization of a polyester polyol obtained by reaction between a specific diol component and a polybasic acid component; a (meth)acrylate having a hydroxyl group; and a polyisocyanate. The document describes that because of containing the oligomer, the composition can show high photocuring properties and high heat resistance even when it includes highly water absorptive acryl monomers such as N-vinylpyrrolidone or when the concentration of urethane groups is increased.
Further, JP-A-2000-204125 (Patent Document 4), JP-A-2001-200007 (Patent Document 5) and JP-A-2004-014327 (Patent Document 6) disclose that urethane acrylate compounds having specific chemical structures provide high heat resistance.
However, according to the description in these documents, the synthesis of urethane compounds entails any of high reaction temperature, long reaction time, and use of environmentally hazardous tin catalyst. These unfavorable factors must be improved.